Thread-cutting machines



July 28, 1959 c. E. GUEST 2,896,510

THREAD-CUTTING MACHINES Filed Feb. 13, 1956 6 SSheets-Shet 1 INVENTOR. I 6242/0515 6-1055? July 28, 1959 c. E. GUEST 2,395,510

. THREAD-CUTTING MACHINES Filed Feb. 15, 1956 5 Sheets-Sheet 5 INVENTOR. 62/9005 15' 0557 W ffwma July 28, 1959 c E, UEST 2,896,510

THREAD-CUTTING MACHINES Filed Feb. 13, 1956 5 Sheets-Sheet 4 INVEN MR. (20005 5 M55 7' BY 15M swim/r m y 23, 1959 c. E. GUEST THREADCUTTING MACHINES Filed Feb. 15, 1956 I 3 w n n M u Ur m 3 IL. WWW. M y w a I h w W WEE u unllml i|- I n t .u n w m" n L r I, m rg H it IN VEN TOR. 6201/05 Z. 625s;-

United States Patent THREAD-CUTTING MACHINES Claude Guest, Springfield, Mass; Myrtice E. Guest, executrix of said Claude E. Guest, deceased, assignor of one-half to Myrtice E. Guest and one-half to Jean A. Enzenbacher, both of Longmeadow, Mass.

Application February 13, 1956, Serial No. 565,210

7 Claims. (Cl. 90--11.56)

This invention relates to thread-cutting machines and aims particularly to provide a machine capable of producing a wide variety of variable-pitch threads.

In thread-cutting machines, the work is rotated about its axis and the tool is traversed along the axis of the work, usually by movement of the tool relative to the work but sometimes by an equivalent movement of the work relative to thetool. In thread-cutting machines heretofore used, the work-rotating drive and the tooltraversing drive have been connected, usually mechanically, to determine their speed relation and thus the pitch of the thread cut on the work. The usual connection is gearing, such as a worm, which provides a'fixed speed ratio between the two drives so that a thread of a fixed pitch is cut. In some thread-cutting machines, variablepitch threads have been produced by providing between the drive for rotating the work and the drive for traversing the tool a mechanical connection adapted to cause apredetermined variation in speed ratio. Such connections have included cams and levers. While they have produced variable-pitch threads, they have proved inadequate to produce many types of variable-pitch thread desired for lead screws, cams and "the like in modern auto matic machinery. It has heretofore been impossible to produce economically complicatedvariable-pitch threads.

My invention overcomes this limitation and provides a thread-cutting machine having the flexibility required for the cutting of all types of variable-pitch threads.

An outstanding feature of my machine lies in the complete independence of the work-rotating drive and the tool-traversing drive. Two separate and independent driving means are used, each with its own source of power, and there is no mechanical orother direct connection between them. Each drive is provided with manually-controlled means for regulating its speed and the two speed-regulating devices are entirely independent of each other. The provision of separate work-rotating caused by the work-rotating drive is transverse to this line.

In the simplest form of my machine, the pattern and the work are moved at the same speed, while the tracer and tool are traversed at the same rate, but it is within the scope of my invention and often more convenient to make the ratio of the work movement and the pattern movement and the ratio of the tracer movement and the tool movement something other than unity, as by this means a single template or pattern may be made to produce screws of different sizes and also threads of diflerent pitches.

In order that my invention may be clearly understood, I will describe the specific embodiments of it which are shown in the accompanying drawings, in. which:

Fig. 1 is a plan view of a thread-cutting machine embodying the invention in a complete form;

Fig. 2 is a side elevation sectioned on the line 2-2 of Fig. 1 showing the programing device forming part of the machine of Fig. 1;

Fig. 3 is an enlarged end elevation sectioned on the lines 3-3 of Fig. l and Fig. 5 and showing the motor for rotating the work;

Fig. 4 is a transverse section on the line 44 of Figs. 1 and 6 showing the tool carriage;

Fig. 5 is an end elevation sectioned on the line 5'-5 of Fig. 1 and containing a front elevation of the proand tool-traversing drives which are separately conthread is to have at each point along the axis of the work may be adapted for use in my machine.

In the form of my invention which I consider most desirable, the programing means includes a template or pattern moved by the drive for rotating the work and a feeler or tracer moved by the tool-traversing drive. The pattern has an edge whose distance from a base line indicates the desired pitch. The traverse of the tracer caused by the tool-traversing means is along this base line, while the movement of said edge. of the pattern graming device forming part of the machine of Fig. 1;

Fig. 6 is a side elevation of the machine shown in Fig. l sectioned on the line 6-6 of Fig. 1;

Fig. 7 is a detail of one of the work bearings sectioned on the line 77 of Fig. 6;

Fig. 8 is a diagram indicating the relation between the template with the thread cut on the work;

Fig.9 shows the thread cut on the work of larger diameter with the use of the same template;

Fig. 10 shows a thread which could be cut on the work by means of the same template by moving the rate of movement of the tracer twice that of the tool carriage;

Fig. 11 is a diagram of an electric circuit of the workrotating motor;

Fig. 12 is a diagram of the electric circuit of the traversing motor;

Fig. 13is a plan view of a simplified threadcu'tting machine embodying the invention;

Figs. 14, 15, 16 and 17 are sections on the lines 14-14, 15-45, 16-16 and 17-17 of Fig. 13;

Fig. 18 is a section of a thread-cutting machine differing from those previously shown in a change in the form of the programing means;

Fig. 19 is an elevation of thread-cutting apparatus partially mounted on the work table of a milling machine;

Fig. 20 is a vertical section of the work table shown in Fig. 19 showing also a tool and tracer with fixed mountings; and

Fig. 21 is an elevation of the movable carriage at the right-hand end: of Fig. 19. i

The thread-cutting'machine shown in Figs. 1-l2, like other thread-cutting machines, has work and tool holders which provide for rotation of the work and traverse between the tool and the work. The work holders include split'collars 10 detachahly secured on a round bar or rod w which constitutes the work, and fixed bearings llfor these bushings mounted in end frames. 12, 13. The tool holder consists of a carriage B5 mounted on longitudinalways consisting of bars 14 and 15 (shown in Figs. 3 and 6,.but omitted in Fig. 1 for the sake of clarity) extending between theend frames 12, 13 and parallel to the axis of the work w. The tool 20 is shown as a rotary u cutter and is fixed on theshaft of a motor .21 mounted on the tool carriage B5. The carriage B'5 104, 104 fixed on the uprights 101, 101.

10 attached. The machine illustrated is a duplex machine having a second work w mounted in the end frames 12, 13 parallel to the work w; and a second tool 20 mounted on the tool carriage B to operate on work w.

The machine has independent drives for causing rota- 1 tion of the work and traverse between the tool and work. An electric motor A causes rotation of the work by driving a pinion A2 fixed on the work w, through reduction gearing A1. The second work w is rotated by the same motor through a sprocket chain A3 which connects sprockets A4 and A4 fixed on the work rods w and w. A rheostat 30 is provided for controlling the speed of the motor A. An entirely independent electric motor B causes the traverse of the tool 20 by driving an endless chain B3 which extends between sprockets the motor B which is connected by beveled-gears B7 B2, B4 on the end frames'12, 13 of the machine and hasits upper reach secured to the tool carriage B5. Reducing gearing B1 connects the motor B with a driving sprocket B2 at one end of the chain B3. A rheostat 40 is provided to control the speed of the motor B.

As the work-rotating drive and the traverse drive are entirely independent, threads of a wide variety of varying pitches may be cut onthe work by manual control of the speed of one or both of the independent driving motors A, B by means of the rheostats 30, 40. While my machine may be used in this way, an important fea ture of my invention consists in programming means for controlling the pitch of the thread cut on the. work.

mesh with racks A16, A16 plate A17.

In the form shown, the parts of the connecting mechanism are such that the plate A17 and template 50 are moved downward at a rate equal to the rate of the rotary movement of the periphery of the work bar w. By substituting sprockets of different size for the sprockets A9 and All, the movement of the template may be given any desired ratio to the peripheral movement of the work w. The clutch 103 provides means for setting the template in a desired position without moving the work,

The tracer 60, which may be of the type used in copying machines, is moved parallel to the base line 52 of the template 50 by means of the motor B which causes the traverse of the tool 20. .The tracer 60 is mounted on a block B15 containing two transverse bores which slide on parallel horizontal rods 105, 105' fixed in the brackets 104, .104. The movement of the tracer is thus parallel to the horizontal base line 52 of the template .50.

. The connection between the traversing motor Band the tracer 60 includes an extension B6 of the shaft of secured to the back of the with a short shaft B8 onwhich is mounted a sprocket B9 connected by a chain B10 to a sprocket B11 freely mounted on a short shaft B12 which has a bearing at one end in the bracket 104 and at the other end in an upright 106. The sprocket B11 may be fixed to the a sprocket B13 on the shaft B12 and an idler sprocket 108 on the bracket 104' fixed on the post 101'. The

3 ends of the chain B14 are fixed to the block B15 which In the form illustrated in Figs. 1-12, the programing means consists of a pattern or template 50 and a tracer 60. The template has an edge 51 which indicates by its distance from successive points of a base line 52 the pitch which the thread is to have at each point along the axis of the work. Distances from the base line 52 to the edge 51 indicate circumferential distances of the thread from its original circumferential position. Thus, the edge 51 is formed in such a way that'if the template were made of paper or other flexible material so that it could be wrapped around the work w or w, the edge 51 would then form the desired thread curve.

The template 50 is moved transversely to its base line 52 by the work-rotating motor A. The template 50 is mounted on a vertical plate A17 which has fixed at its four corners bearings 100 which slide on vertical rods 101, 101' connected at their tops by a cross bar 102 and forming part of the frame of the machine. Since the base line 52 of the template is horizontal in the form shown, vertical movement of the plate A17 to which the template is attached is line 52.

The connection between the work-rotating motor A and the plate A17 carrying the template includes the .work bar w which, as hereinbefore explained, is rotated by the motor A. It is, however, not necessary that the work bar should constitute a part of the connection between this motor and the template. In the form shown, a sprocket A5 fixed on the work w is connected by a perpendicular to the base chain A6 to a sprocket A7 fixed on a stub shaft A8. 1

sprocket A9 is connected by a chain A10 to a sprocket All on a short stub shaft A12 connected through beveled gears A13 to a shaft A14 mounted in hearings in brackets Near the endspf the cross shaft A14 are pinions A15, A15 which carries the tracer 60. r

The parts of the connecting mechanism illustrated make the rate of movement of the tracer equal to the rate of movement of the tool carriage which is also driven by the motor B. The ratio of the movement of the carriage to the movement of the tracer may be changed by substituting sprockets of different sizes for the sprockets B9 and B11.

The programing means controls the relative speed of the motors A and B by means of electric connections illustrated in Fig. 12. The tip 61 of the tracer 60 is spring biased by spring 62 toward the edge 51 of the template. When the pressure of the template against the tracer is sufiicient to overcome the force of the spring, a switch 63 is opened. This acts through a relay 64 to cut off the supply of electricity to the traversing motor '3. The motor, starts again when the pressure on the tip is re duced.

The use and, operation of the machine which has been described is as follows:

The collars 10, the sprockets for the chain A3, the sprocket A5 and the gear A2 are clamped to the work .bars w, w. The upper sections of the end frames 12 and 13 and of'the carriage B5 are removed and the Work bars are placed in position as shown in Figs. 1 and 6, after which the upper sections are replaced.

The carriage B5 is moved to the end of the bars 14, 15 which are uppermost in Fig. 1 and to the left in Fig. 6, that is, to the end of the bars near the sprocket A5. The clutch 103 is opened and the plate A17 carrying the template 50 is moved to its lowest position indicated by dotted lines in Fig. 5 after which the clutch 103 is closed. The clutch 107 is opened and the block B15 is moved to the left in Fig. 5 to bring the tracer to a posi tlon under the end of the edge 51 of the template as shown by the dotted circle atthe left side of Fig. 5.

The motors A and B are then started and their speeds are controlled manually in such a way as to make the tracer 60 move along and press against the edge 51 of the template. In this manual control, the traversing motor B is operated somewhat more rapidly than would be necessary to keepthe tracer in uniform contact with spa m the edge 51. The traversing movement is fast enough so that the tracer is intermittently pressed against the edge 51 sufiiciently to open the switch 63 and stop the motor B. The rotary movement caused by the motor A is continuous, and, as soon as it has had the effect of relieving the pressure on the tracer 60, the traversing motor B goes into operation again. This intermittent stopping of the traversing motor B makes the average rate of traverse hear such relation to the rate of rotation caused by the motor A that the tracer follows the edge 51 and a thread having the required pitch at each point is produced on the work. It will, of course, be realized that the start and stop mechanism in the circuit to the motor B is extremely sensitive so that, while the traversing motor operation is intermittent the cut in the work is made as a substantially smooth curve.

When the tracer 60 has reached the right-hand end of the edge 51 of the template and the template is in its raised position as shown in [full lines in Fig. 5, the machine is stopped. The template 50 may then be replaced by another template, the template and tracer returned to their starting positions by the use of clutches 103 and 107 and the operation repeated. Completion of traverse of the tracer may leave the carriage B5 adjacent end frame 13 but at some distance from the ends of the work rods. In this case the work rods may be advanced and the carriage moved back toward end frame 12 and the operation repeated. Thus a thread of a predetermined variable pitch may be out upon rods of indefinite length.

The relation between the thread cut on the Work and the edge 51 of the template is shown in Fig. 8. By making the transverse movement of the template only half the peripheral movement of the work w, as, for example, by doubling the diameter of the work w, a steeper thread may but cut with the same template as shown in Fig. 9. By changing the sprockets B9 and B11 to make the movement of the tracer twice as rapid as the movement of the carriage, it is also possible to cut the steeper thread on the original rod as shown in Fig. 10.

When the ratio between the rate of movement of the template and the peripheral speed of the work and the relation between the rate of movement of the tracer and the rate of movement of the carriage are kept the same, the ratio determines the relation between the scale of the template and the scale of the thread cut on the work. It is often convenient to make the scale of the template smaller by making the template movement and the tracer movement slower than the movements of the work and tool; but, when great accuracy is required, there is an advantage in making the scale of the template greater than the scale of the work by making the movement of the template and the movement of the tracer faster than the movement of the work and the movement of the tool.

It is apparent that other electric controlling circuits may be used with the programing device, for example, a circuit changing the speed of one or both of the motors A, B so as to obtain the speed ratio between them required to make the tracer follow the edge 51 without stopping either of them and without any manual control of either of them.

For less accurate work, the control circuit of the programing device may be omitted and the programing means may serve merely as a visual indicator for guiding manual control of the speed of the motors A and B. It is apparent that if the speed ratio of the motors is continually adjusted so as to make the tracer follow the edge 51 of the template, the tool will out the desired thread on the work.

-A simplified: thread-cutting machine embodying the invention is shown in Figs. 13 to 17. In this machine, the traversing movement of the tracer is at the same rate asthe traversing movement of the tool. This precludes the use of a pattern of a different scalefrom that of the work but it leads to a considerable simplification. By positioning the template of the programing means so :that its base line is parallel to the axis of the work, both the direction and rate of the tracer traverse are made the :same as the direction and rate of traverse of the tool. This permits connecting the tracer with the traversing drive by the simple expedient of mounting it directly on the tool carriage.

, The simplified machine shown in Fig. 13 has end frames 12.1, 13.1 similar to those shown in Fig. 1 but the uprights supporting the programming mechanism are omitted.

The tool carriage B51 is mounted as in Fig. l but the second tool shown in Fig. 1 is replaced by a tracer 60.1 similar to the tracer 60 which is adjustably mounted on the tool carriage.

The template 50.1 is moved horizontally instead of vertically as shown in Fig. 1. The template is mounted on a strap A17.1, the opposite ends of which are fixed to a pair of movable rack bars A161, A161 supported on each end frame 12.1 and 13.1 respectively. Asbest seen in Figs. 16 and 17, the rack bars are slidably mounted on the top walls of the end frames 12.1 and 13.1 and extend through slots therein for meshing engagement with pinions A15.1, A15.1' fixed on a shaft A141 extending between ttie end frames. This shaft may be mounted in bearings in the end frames similar to'those in which the second work w is mounted in Fig. 1.

Independent motors A and B rotate the Work w and cause the traversing movement of the tool 20.1 in the same way as in Fig. 1. The work-rotating motor A is connected to move the template 50.1 by a sprocket chain A31 connecting the sprocket A4.1 on the work shaft with the sprocket A4.1' on the shaft carrying the gears A15.1, A15.1' which mesh with the racks A161, A161 on the template 50.1. The connection between the traversing motor B and tracer 60.1 is obtained merely by mounting the tracer 60.1 on the tool carriage B51 which is moved by the traversing motor B.

It is apparent from the above description that the machine of Fig. 13 may be used in the same way as the machine of Fig. l, but that it is less versatile in that a 1:1 ratio is maintained between the tool movement and the tracer movement and between the peripheral movement of the work and the template movement.

The thread-cutting machine shown in Fig. 18 difiers from that just described in the use of a different programing device. Instead of using a flat template with a plane curve, indicating the pitch of the thread to be cut, use is made of .a cylindrical pattern containing a groove or thread whose pitch it to be duplicated in the thread cut on the work. In this pattern, the base line is a line on the surface of the cylinder parallel to its axis, and the circumferential distances from this line to the groove or thread in the pattern represent the corresponding circumferential distances of the thread to be cut on the work from its initial circumferential position. The pattern is rotated by the work-rotating drive. The tracer engages one edge of the groove in the pattern and is moved parallel to the axis of the pattern by the tool-traversing drive.

The machine shown in Fig. 18, however, is of the simplified type shown in Figs. 13 to 17 with the tracer mounted on the tool carriage and the base line of the pattern parallel to the axis of the work.

The thread-cutting machine shown in Fig. 18 is like those which have been described except that a grooved pattern bar 50.2 is substituted for the second bar w of Fig. 1 and the pinion shaft A14.1 of Figs. 13 and 14, and the tracer 60.2 is mounted on the tool carriage B5.2 in such a position that its tip 61.2 engages one edge of a groove 5 1.2 contained in the pattern bar 50.2.

d This machine operates in a manner similar to those described in that the contact between the tracer and one side of the groove in the pattern bar controls the traversing motor so that the groove cut in the work bar w' has the same pitch at each point as the groove in the pattern bar.

Figs. 19 to 21 show a thread-cutting device which differs from those previously described in that the tool and work traverse is obtained by movement of the work with respect to the tool instead of by movementof the tool with respect to the work. These figures show the table member 120 of a milling machine. It is wellknown that the table of such a machine is provided with conventional ways and a reciprocating drive (not shown) for endwise travel back and forth.

The table 120 is provided with an extension consisting of an I-beam 121 supported in tracks orspaced rail members 122 suitably mounted in an elongated bed support as indicated at 123, extending endwise from the table 120 adjacent to the base thereof. Clamping plates 124 boltedto the table 120 in a lower T-slot 1Z5 releasably clamp the extension 121 to hold the same fast to the table while the table is reciprocating. Thus movement of the table 120 to the left in Fig. 16 moves the extension 121 to the left and with it an end carriage 126 which is mounted on the extension near its end.

The work w and a jack shaft A14.3 similar to that shown in Figs. 13 and 14 are rotatably mounted in bearings secured to the table 120 and the end carriage 126. A motor A3 for rotating the work and the jack shaft is also carried in the end carriage 126; V

A template 50.3 and racks A16.3, A163 and pinions A153, A153 connecting it with the jack shaft A143 are also mounted on the table 120. Thus it will be seen that, as the table 120 moves to the left, both the work w and the template 50.3 also move towards the left. A thread-cutting tool 20.3 and a tracer 60.3 are mounted on a fixed column 130 adjacent to the table 120 so that they engage respectively the work w and the curved edge 51.3 of the template 50.3. The traverse of the tool and work dependent driving means for causing relativetraverse between the tool and work, a cylindrical pattern containing a spiral groove of variable pitch in the cylindrical surface, operative means from the first driving means pattern, and means controlled by contact between the tracer and said edge of the groove in the pattern to regulate the relative speed of the two driving means to produce a thread of variable pitch corresponding to that of the groove of the pattern.

3. A thread-cutting machine comprising a rotatable work holder, a tool, a tool carriage movable parallel to the axis of the work, a pattern having a base line parallel to the axis of the work and an edge indicating the pitch of the thread to be cut on the work and mounted for movementof its surface transverse to its base line, a tracer mounted on the tool carriage and engaging said edge of the pattern, a drive connected to the work holder and the pattern to rotate the work holder and cause such transverse movement of the pattern, and an independent drive connected to cause a traversing movement of the tool carriage, and means controlled by contact between the tracer and the pattern to regulate the relative speed of the two driving means to cut a thread of the pitch indicated by the pattern.

4. A thread-cutting machine for cutting threads on rods of indefinite length comprising two widely separated end posts each consisting of upper and lower separable parts, a bearing in each post split at the juncture of its upper and lower parts, split bearings detachably secured to the work and engageable in the bearings of the and the traverse of the tracer and template are thus caused by longitudinal movement of the .work and the template, while the tool and tracer remain stationary. This does not change the relative traverse between the tool and work and between the tracer and template which remains as in the machines previously described. i In this arrangement, the motor of the milling machine which moves the table 120 is the traversing motor of the thread-cutting device and is controlled like the traversing motor B shown in the other embodiments by an electrical connection from the tracer which is illustrated in Fig. 12.

In all the thread-cutting machines described, the traversing motor B is reversible (see Fig. 12), so that, in addition to cutting continuously progressing thread grooves like that shown in Fig. 1, the machines may be used to cut crossing threads or grooves in the form of closed loops of elliptical or other shape.

This application is a continuation-in-part of my application filed March 22, 1954, Serial No. 417,727, and of my application filed July 1, 1954, Serial No. 440,798, both applications being now abandoned.

What is claimed is:

1. A thread-cutting machine comprising a driving means for rotating the work, a cutting tool, a second independent driving means for causing relative traverse between the tool and work, a pattern having an edge indicating by its distance from a base line the pitch of a variable-pitch thread to be cut upon the work, a tracer engageable with said edge of the pattern, operative means from the first driving means to the pattern to move the pattern transverse to said base line, a connection. between the second driving means and the tracer to move the tracer parallel to the base line of the pattern, and means controlled by contact between the tracer and the pattern to regulate the relative speed of the two driving means to produce a thread of the pitch indicated by the pat tern.

2. A thread-cutting machine comprising a driving means vfor rotating the work, a cutting tool, a second inposts, a guide way between the posts, a tool carriage slidably mounted on said guideway and consisting of separable upper and lower parts, a bearing in said carriage split at the juncture of its upper and lower parts and adapted to fit and slide upon the work, and a rotary thread-cutting tool mounted on the carriage to engage the work near the point at which the work passes through the bearing in the carriage.

5. A thread-cutting machine comprising a rotatable work holder, a tool holder having a cutting tool, and a traversing mechanism for causing relative movement between the tool and the work along the axis of the work holder, two independent driving means, means connecting one driving means to the Work holder to rotate the same, independent means connecting the other driving means to the traversing mechanism to operate the same, and independent speed controls for the two driving means, so that by varying the speed of one or both of the driving means a great variety of variable-pitch threads may be cut on the work.

6. A thread-cutting machine comprising a first driving means for rotating the work, a cutting tool, a second driving means for causing relative traverse between the tool and the work, independent speed controls for the two driving means, a pattern having an edge indicating by its distance from a base line the pitch of a variablepitch thread to be cut on the work movable by one of the driving means, a tracer engageable with said edge of the pattern movable by the other of the driving means, the tracer being" spring biased into engagement with the edge of the pattern, and means operative in response to frictional force between the tracer and the template suificient to overcome the force of the spring to regulate the relative speed of the two driving means to produce a thread of the pitch indicated by the pattern.

7. A thread-cutting machine comprising a first driving means for rotating the work, a cutting tool, a second driving means for causing relative traverse between the tool and the work, independent speed control means for the two driving means, a pattern having an edge indieating by its distance from a base line the pitch of a variable-pitch thread to be cut on the work movable by the first driving means relative to said work, a tracer engageable with said edge of the pattern movable by the second driving means along the edge of the pattern, the tracer being spring biased into engagement with the edge of the pattern, and means operative in response to frictional force between the tracer and the template sufficient to overcome the force of the spring to regulate the relative speed of the two driving means to produce a 10 2,754,711

thread of the pitch indicated by the pattern.

Palmer Mar. 3, 1885 16 10 Ross Oct. 9, Shaw et a1. Aug. 5, Saives Aug. 30, Kopp July 13, Miller May 14, Barnes Dec. 24, Johnson Apr. 24, Johnson July 8, De Vlieg et al. Dec. 1, Shapiro et al. July 17,

OTHER REFERENCES American Machinist, June 20, 1955, vol. 99, No. 13 (p. 143 relied on). 

